A callback mechanism for Private Telecommunications Networks

Ming-Feng Chang*, Fang Sun Lu, Chung Yung Chia

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Private Telecommunications Networks (PTNs), such as enterprise telephony and Voice over IP (VoIP), have been widely deployed. A common limitation of PTNs is that PTN users are usually not assigned with Public Switched Telephone Network (PSTN) E.164 numbers. A PTN user is usually identified by an extension number or a URI (universal resource identifier). When a PTN user initiates a call to a PSTN user, it is not possible to use the PTN calling party's identifier as the caller ID; instead, an E.164 number of the PBX or VoIP gateway is used. As a result, the PSTN called party cannot use the caller ID received to call back to the PTN calling party later, if the PTN user's extension number or URI is unknown. This paper proposes a callback table approach to solve this problem. We describe how the call-out information is stored into and retrieved from a callback table maintained in the PBXs or VoIP gateways to provide callback service. Numeric analysis has been performed to evaluate the performance of this callback solution. The numeric results indicate that the callback method provides a satisfactory solution when there is sufficient voice traffic served by a VoIP gateway.

Original languageEnglish
Pages (from-to)583-588
Number of pages6
JournalComputer Communications
Issue number5
StatePublished - 15 Mar 2010


  • Callback
  • PSTN
  • VoIP
  • VoIP gateway

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